<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>CSS 框模型 (Box Model)</title>

    <style type="text/css">
        div {
            background-color: red;

            height: 70px;
            width: 70px;

            line-height: 70px;
            text-align: center;

            /* “80 * 80” = width * padding * 2 + border *2 = 70 + 5 * 2 + 0 *2 = 80 = 背景*/
            padding: 5px;
            margin: 10px;
        }
    </style>
</head>
<body>

    <p>123456</p>
    <div>
        div
    </div>
</body>
</html>